Evaluating stiffness of gastric wall using laser resonance frequency analysis for gastric cancer.

Tumor stiffness is drawing attention as a novel axis that is orthogonal to existing parameters such as pathological examination. We developed a new diagnostic method that focuses on differences in stiffness between tumor and normal tissue. This study comprised a clinical application of laser resonance frequency analysis (L-RFA) for diagnosing gastric cancer. L-RFA allows for precise and contactless evaluation of tissue stiffness. We used a laser to create vibrations on a sample's surface that were then measured using a vibrometer. The data were averaged and analyzed to enhance accuracy. In the agarose phantom experiments, a clear linear correlation was observed between the Young's modulus of the phantoms (0.34-0.71 MPa) and the summation of normalized vibration peaks (Score) in the 1950-4050 Hz range (R² = 0.93145). Higher Young's moduli also resulted in lower vibration peaks at the excitation frequency, signal-to-noise (S/N) ratios, and harmonic peaks. We also conducted L-RFA measurements on gastric cancer specimens from two patients who underwent robot-assisted distal gastrectomy. Our results revealed significant waveform differences between tumor and normal regions, similar to the findings in agarose phantoms, with tumor regions exhibiting lower vibration peaks at the excitation frequency, S/N ratios, and harmonic peaks. Statistical analysis confirmed significant differences in the score between normal and tumor regions (p = 0.00354). L-RFA was able to assess tumor stiffness and holds great promise as a noninvasive diagnostic tool for gastric cancer.